Side-injected metal refining vessels, although a comparatively recent development, are widely used in such industries as the steelmaking industry because of the high mixing energy which is imparted to the bath to achieve both a conducive gas-liquid interfacial surface area and gas residence time for efficient gas-liquid reactions. In addition, side injection permits the tuyeres to be raised out of the bath during inactive periods of processing thus conserving process gas. Side injection may be the sole means of injecting gases into a metal melt or it may be employed in conjunction with another means of providing gases to a melt, such as with a top lance.
A significant expense in a metal refining process, such as steelmaking processes wherein gases are injected into the melt from below the melt surface, is the consumption of refractory in the area proximate the point of the gas injection due to the high heat of the oxidation reactions and erosiveness of the turbulent liquid metal reaction proximate the point of injection. In the case of a side injection metal refining process, the refractory consumption problem is manifested most prominently at the side of the metal refining vessel in the area proximate the injection point.
Those skilled in the art have addressed this problem by increasing the thickness of the refractory lining in the area proximate the gas injection point. Thus, for a bottom-injected vessel the refractory is considerably thicker at the bottom of the vessel than it is at its sides. This solution to the problem of local high refractory wear rate has been successfully implemented with side-injected vessels.
It is desirable that the lining of a metal refining vessel wear in such a way that no one portion of the lining wears out significantly before the other portions. It has been observed that refractory linings of side-injected steelmaking vessels unexpectedly tend to wear out in the area above the side injection point while the other portions of the lining still have considerable thickness remaining. This is undesirable and costly since the unconsumed lining must be discarded and the vessel relined because of the early failure of the lining in the area above the injection point. This failure mode is not expected since one would expect the higher wear rate to be in the side area proximate the gas injection point and not in the side area above the gas injection point.
At first glance it might appear that the solution to this problem is not difficult. By applying the known expedient, i.e., increasing the lining thickness in the area of high wear rate, one could sucessfully address this problem. However, such a solution has two disadvantages. First it greatly increases the amount of refractory lining used and thus further increases the cost of metal refining. Second, it reduces the volume within the vessel available for the molten metal, thus requiring the refining of a smaller amount of metal per heat, slower injection of gases into the melt or the refining of the metal with an increased risk of overflow or slopping because of the necessarily higher level of the bath surface within the vessel during gas injection.
Therefore it is desirable to have a side-injected metal refining vessel wherein the refractory lining in the side area above the injection point does not wear out significantly earlier than other lining areas, such as in the side area proximate the injection point, without the need for a thicker lining above the injection point than proximate the injection point.
Accordingly, it is an object of this invention to provide an improved side-injected metal refining vessel.
It is a further object of this invention to provide an improved side-injected metal refining vessel wherein greater economy of refractory lining usage can be attained over that possible with heretofore available conventional side-injected metal refining vessels.